This week in our series, we continue the story of the United States Constitution.In May of 1787, a group of America's early leaders met in Philadelphia, Pennsylvania to amend the Articles of Confederation.That document had established a loose union of the 13 states with a weak central government.But instead of amending the articles, the delegates at the convention wrote a completely new constitution.As we heard last time, one of the issues they discussed was slavery.The existence of slavery affected decisions like how to count the national population. It also affected the powers proposed for Congress.